Stress in polyimide coatings

The effect of film thickness on in-plane molecular orientation and stress in polyimide films prepared from pyromellitic dianhydride with 4,4′-oxydianline was investigated using a prism coupling technique to measure the refractive index. Film thickness was controlled by varying both solution concentration and spinning conditions. Birefringence, the difference between the in-plane and out-of-plane refractive indices, was used to characterize the in-plane molecular orientation. The observed birefringence is a combination of the birefringence resulting from molecular orientation and the birefringence induced by the residual stress present in the films. The birefringence decreases with increasing film thickness over the range of thicknesses studied (3–20 μm) indicating that the molecular orientation decreases with increasing film thickness. The in-plane coefficient of linear thermal expansion (CTE), controlled by the level of orientation in the film, increases from 18 to 32 × 10^?6/°C over the same thickness range. The birefringence of free-standing films was lower than that of adhered films due to the release of residual stress in the film once the film is removed from the substrate. The residual film stress arises primarily from the mismatch in CTEs between the polyimide film and the substrate to which the film is adhered. Thus, since the film anisotropy decreases with increasing thickness, the film stress increases with increasing thickness. Residual stress calculated by integrating the product of the film modulus and the CTE mismatch assuming temperature-dependent properties is comparable to experimentally measured film stress. Ignoring the temperature dependence of the film properties leads to an overestimation of stress. Moisture uptake was used to study the stress dependence of the optical properties. Moisture uptake increases both the in-plane and out-of-plane refractive indices by equal amounts in free-standing films due to an isotropic increase in the polarizability. In adhered films, an increase in moisture uptake leads to a decrease in the birefringence due to a swelling-induced decrease in the residual film stress. © 1994 John Wiley & Sons, Inc.     

The effect of orientation on thermal expansion behavior in polyimide films

The anisotropy of the thermal expansion of polyimide films was investigated . Out-of-plane or thickness direction coefficients of linear thermal expansion (CTE) were calculated from the difference between the coefficient of volumetric expansion (CVE) and the sum of the in-plane or film direction coefficients of linear thermal expansion for commercial and spin-coated PMDA//ODA and BPDA//PPD films and spin coated BTDA//ODA/MPD films. The CVEs were obtained from a pressure-volume-temperature (PVT) technique based on Bridgeman bellows. The CVE was shown to be essentially constant, independent of molecular orientation and thickness. A decrease in the in-plane CTEs therefore occurs at the expense of an increase in the out-of-plane CTE. In all cases the calculated out-of-plane CTE was higher than the measured in-plane CTE. The ratio of the out-of-plane CTE to the in-plane CTE was 1.2, 3.8, and 49.3 for the spin-coated BTDA//ODA/MPD, PMDA//ODA, and BPDA//PPD films, respectively. © 1994 John Wiley & Sons, Inc.     

Poly(ester imide)s possessing low coefficients of thermal expansion (CTE) and low water absorption (III). Use of bis(4-aminophenyl)terephthalate and effect of substituents

A variety of poly(ester imide)s (PEsIs) were prepared using bis(4-aminophenyl)terephthalate (BPTP) and substituted BPTP (BPTP series) for applications to novel base film materials in flexible printed circuit boards (FPC). BPTP series were all highly reactive with various tetracarboxylic dianhydrides and led to considerably high molecular weights of PEsI precursors. The thermally imidized BPTP-based PEsI films achieved lower extents of water absorption (W_A) than the corresponding 4-aminophenyl-4′-aminobenzoate (APAB)-based PEsI systems while keeping other target properties, in particular, the linear coefficient of thermal expansion (CTE) much lower than that of copper foil as a conductive layer in FPC. The lower W_A is attributed to the decreased imide contents in the structure by using BPTP. The considerably low CTE can be explained in terms of intimate stacking between the p-aromatic ester fragments with an extended conformation. The BPTP-based PEsI system also exhibited a considerably low dissipation factor (tan δ = 1.91 × 10⁻³) at a high-frequency electric field of 18.3 GHz, comparable to a liquid-crystalline polyester. An effect of substituents on the film properties was also investigated in this work. Incorporation of methyl substituents on BPTP was very effective for property improvement, whereas methoxy substituents on BPTP, as well as methyl substituents onto hydroquinone bis(trimellitate anhydride) (TAHQ), showed a trend to significantly increase the CTE. Copolymerization with an adequate amount of a typically flexible monomer, 4,4′-oxydianiline (4,4′-ODA), allowed the CTE matching with copper foil and the film toughness improvement at the same time. The PEsI copolymer prepared from TAHQ (10 mmol) with methyl-substituted BPTP (7 mmol) and 4,4′-ODA (3 mmol) achieved excellent combined properties, namely, a very high T_g at 410 °C, a slightly lower CTE (10.0 ppm/K) than that of copper foil, suppressed water absorption (0.35%), an extremely low linear coefficient of humidity expansion (CHE = 3.4 ppm/RH%), and good film toughness (the elongation at break, ε_b = 50.7%). Thus, BPTP- and methyl-substituted BPTP-based PEsI systems can be promising candidates as a next generation of FPC base film materials.     

柔性OLED用高耐热聚酰亚胺薄膜的制备与性能

聚酰亚胺(PI)薄膜作为柔性有机发光显示(OLED)基板材料应用时, 需要满足玻璃化转变温度(T_g)大于450 ℃和热膨胀系数(CTE)在0~5×10^-6 K^-1之间. 为了提高PI薄膜的热性能, 本文合成了2,7-占吨酮二胺 (2,7-DAX), 并将其与均苯四甲酸二酐(PMDA)和2-(4-氨基苯基)-5-氨基苯并噁唑(BOA)共聚制备了一系列新型PI薄膜. 研究了PI薄膜的聚集态结构、 耐热性能、 尺寸稳定性和力学性能. 结果表明, 占吨酮结构和苯并噁唑结构提高了PI分子链的刚性与线性, 使分子链在平面内紧密堆积与取向, 制备的PI薄膜综合性能优异, 玻璃化转变温度高于408 ℃, CTE在-5.0×10^-6~8.1×10^-6 K^-1之间, 拉伸强度大于140 MPa, 拉伸模量大于4.2 GPa, 断裂伸长率为7.1%~20%, 5%热失重分解温度(T_5%)在601~624 ℃之间. 其中, PI-50和PI-60薄膜具有超高玻璃化转变温度和超低热膨胀系数, T_g高于450 ℃, CTE分别为2.1×10^-6 K^-1和1.6×10^-6 K^-1. 制备的系列PI薄膜作为柔性OLED基板材料有潜在应用前景.     

Spontaneous molecular orientation of polyimides induced by thermal imidization (6). Mechanism of negative in-plane CTE generation in non-stretched polyimide films

The mechanism of negative coefficient of thermal expansion (CTE) generation for non-stretched polyimide (PI) films is proposed in this work. Negative CTE behavior was observed in some miscible binary blend films composed of a major fraction of a rod-like semi-crystalline PI derived from pyromellitic dianhydride (PMDA) with p-phenylenediamine (PDA) and flexible PIs based on 2,3,3′,4′-biphenyltetracarboxylic dianhydride (a-BPDA) whereas homo PMDA/PDA PI film shows a considerably low but a positive CTE value. The results suggest that the negative CTE generation is related to not only a considerably high extent of in-plane orientation of the PMDA/PDA chains but also to the crystallinity of the blends. The present work revealed that some other PIs, a poly(ester imide), and a polybenzoxazole system also display negative CTE and these systems also possess extremely high extents of in-plane chain orientation without exception. In addition to CTE, the morphologies were monitored as a function of imidization temperature for two PI systems, PMDA/2,2′-bis(trifluoromethyl)benzidine and PMDA/m-tolidine by wide-angle X-ray diffraction, FT-IR spectroscopy, birefringence, and film density measurements. The results suggested that the negative CTE phenomenon occurs when PI films possess very high extents of in-plane orientation and a less crystalline morphology simultaneously, thereby significant thermal expansion can be allowed to the thickness direction.     

Spontaneous molecular orientation of polyimides induced by thermal imidization (5). Effect of ordered structure formation in polyimide precursors on CTE

Six poly(amic acid) (PAA) systems based on pyromellitic dianhydride (PMDA) formed some ordered structures with optical anisotropies clearly detectable on an optical polarizing microscope (POM) in N-methyl-2-pyrrolidone (NMP) at room temperature at high solute concentrations (15-25 wt.%) with complete sol-gel transition reversibility, whereas PAA systems based on 3,3′,4,4′-biphenyltetracarboxylic dianhydride (s-BPDA) with a variety of diamine components showed no optical anisotropy in solution. However, a fluorescence probe technique combined with solution viscosity measurements suggested that a PAA derived s-BPDA with 1,4-phenylenediamine (PDA), i.e., PAA(s-BPDA/PDA) forms some ordered structure with a POM-undetectable very local scale during prolonged storage in NMP at room temperature. The introduction of the biphenyldiimide (BPDI) units at 33% into the PAA(s-BPDA/PDA) main chains by copolymerization allowed the formation of optically anisotropic gels with a smectic liquid crystal-like ordered structure by cooling the NMP solution at −20 °C. PI films derived from s-BPDA with PDA, i.e., PI(s-BPDA/PDA) were prepared upon thermal imidization of the BPDI-containing PAA films dried at 40 °C for 2.5 h. An increase in the BPDI content caused a gradual decrease in the linear coefficient of thermal expansion (CTE) of the PI films. This can be interpreted as a result of an intensified pre-orientation at the stage of the PAA cast films by incorporation of the BPDI units. When the BPDI-containing PAA solutions were heated at 70 °C for 4 min prior to the drying process at 40 °C, the ordered structures can be cancelled without imidization, and the CTE values of the resulting PI films appreciably increased compared to the case without heating at 70 °C. A similar effect was observed even in the BPDI-free original s-BPDA/PDA system. The results suggest the presence of a POM-undetectable very locally ordered structure in the PAA cast films, which promotes the pre-orientation of the PAA chains in the cast films and consequently can contribute to a further decrease in the CTE of the PI(s-BPDA/PDA) films.     

In situ measurement of the thermal expansion behavior of benzocyclobutene films

In situ measurement techniques suitable for determination of the coefficient of thermal expansion (CTE) in thin, spin‐cast polymer films in both the in‐plane and through‐plane directions are presented. An examination of the thermal expansion behavior of cyclotene thin films has been performed. In particular, the effect of film thickness on the in‐plane and through‐plane CTE and in‐plane Young's modulus of spin‐coated cyclotene films was examined. It is shown that the mechanical response of in situ cyclotene films can be adequately described by isotropic film properties. It was also demonstrated that there is no thickness dependence on the free‐standing mechanical properties or on the resulting through‐plane thermal strain in an in situ film. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 311–321, 1999     

Fabrication of copper–zinc oxide composite thin films from single source precursor by aerosol assisted chemical vapour deposition

A new heterobimetallic complex, Zn₂(OAc)₆(μ-O)₂Cu₄(bdmap)₂Cl₂ (1) where bdmap = 1,3-bis(dimethylamino)-2-propanolato and OAc = acetato, was synthesized by direct interaction of a 2:1.5 mixture of Cu(OCH₃)Cl/Zn(OAc)₂ · 2H₂O with bdmapH in toluene at room temperature and characterized by melting point, elemental analysis, FT-IR spectroscopy, mass spectrometry, thermogravimetric analysis (TGA) and single crystal X-ray diffraction. The aerosol assisted chemical vapour deposition (AACVD) from complex (1) showed that it is a promising precursor to deposit thin films of crystalline Cu–ZnO (2:1) composite. The chemical composition and surface morphology of the deposited thin films were analysed by powder X-ray diffraction (PXRD), scanning electron microscopy (SEM) and energy dispersive analytical X-ray (EDAX), which suggest that the films were thin, crystalline, uniform, smooth and tightly adherent to the substrates with particle size ranging from 0.2–0.5 μm at 250 °C to 0.4–0.9 μm at 475 °C. It was also shown that size of the crystallite can be controlled by controlling deposition temperature of the films. The thickness and voltage–current characteristics of thin films were measured with profilometer and voltmeter by using the four-probe method.     

Achieving structural control with thin polystyrene-b-polydimethylsiloxane block copolymer films: The complex relationship of interface chemistry,annealing methodology and process conditions

The structure of thin microphase-separated polystyrene-block-polydimethylsiloxane (PS–PDMS) films has been studied using state-of-the-art top-down and cross-sectional electron microscopy. This is the first time that the profile of PS–PDMS films has been measured in situ and these measurements allowed us to image the shape of the PDMS domains within the film as well as examine the wetting behavior of the block copolymer film on a variety of substrates. It was found that for each polymer, substrate chemistry and annealing method combination examined, there was a small range of film thicknesses whereby the films exhibited the optimal characteristics of high levels of ordering without dewetting or multilayering. Specifically, the optimum thickness for films treated by thermal annealing was greater than that for the equivalent solvent annealed film; a change that was correlated with morphology variations related to solvent swelling of the solvent annealed films. The surface chemistry also induced changes in the optimum film thickness. Selective surfaces were shown to control whether a PDMS wetting layer was formed or not, leading to either thicker or thinner wetting optimum film thicknesses; while undulating morphologies were observed for less selective surfaces. Concomitant changes in the periodicity were then hypothesized to occur as a result of confinement effects and the selectivity of the surface.     

Highly conformal growth of microstructured polypyrrole films by electrosynthesis on micromachined silicon substrates

A novel technology for fabricating microstructured polypyrrole (PPy) films is presented based on PPy electrosynthesis on micromachined silicon substrates. PPy light-activated electropolymerization is performed on n-type microstructured silicon featuring lattices of square-like pores with pitch of 8 μm, size (s) of 5 μm, and depth (d) from 5 μm up to 50 μm. Scanning electron microscopy (SEM) highlights as light-activation allows a highly conformal polymer growth yielding a three-dimensional PPy structure perfectly replicating the silicon microstructure to be achieved up to high aspect-ratio (HR = d/s). Arrays of highly ordered PPy hollow microtubes with depth up to 50 μm and thickness up to 1 μm are obtained. Chemical analysis of microstructured PPy films is performed by X-ray photoelectron spectroscopy (XPS) and their electrochemical activity is verified by cyclic voltammetry (CV).     

Comparative study of LiMn2O4 thin film cathode grown at high, medium and low temperatures by pulsed laser deposition

LiMn₂O₄ thin films with different crystallizations were respectively grown at high, medium and low temperatures by pulsed laser deposition (PLD). Structures, morphologies and electrochemical properties of these three types of thin films were comparatively studied. Films grown at high temperature (?873 K) possessed flat and smooth surfaces and were highly crystallized with different textures and crystal sizes depending on the deposition pressure of oxygen. However, films deposited at low temperature (473 K) had rough surfaces with amorphous characteristics. At medium temperature (673 K), the film was found to consist mainly of nano-crystals less than 100 nm with relatively loose and rough surfaces, but very dense as observed from the cross-section. The film deposited at 873 K and 100 mTorr of oxygen showed an initial discharge capacity of 54.3 μAh/cm² μm and decayed at 0.28% per cycle, while the amorphous film had an initial discharge capacity of 20.2 μAh/cm² μm and a loss rate of 0.29% per cycle. Compared with the highly crystallized and the amorphous films, nano-crystalline film exhibited higher potential, more capacity and much better cycling stability. As high as 61 μAh/cm² μm of discharge capacity can be achieved with an average decaying rate of only 0.032% per cycle up to 500 cycles. The excellent performance of nano-crystalline film was correlated to its microstructures in the present study.     

Measurement of coefficient of thermal expansion of films using digital image correlation method

Applications of the digital image correlation method (DIC) for the determination the coefficient of thermal expansion (CTE) of films is investigated in this paper. A heating chamber was designed for applying thermal load and DIC provides the full-field thermal deformation fields of the test film sample due to temperature changes. The average normal strains in the x and y direction from the region of interest are then extracted for the determination of CTE. The influence of unavoidable small rigid body rotation is discussed and a method to eliminate it to show the pure thermal expansion of the test film is demonstrated. For validation, the CTE of a pure copper sample is determined and compared with the textbook value, confirming the effectiveness and accuracy of the proposed technique. Finally, the CTE of Polyimide (PI) composite film in the temperature range of 20–140 °C is measured. The results reveal that the DIC is a practical and effective tool for full-field thermal deformation and CTE measurement of films.     

Solution-processable transparent polyimides with low coefficients of thermal expansion and self-orientation behavior induced by solution casting

A fluorinated tetracarboxylic dianhydride (amide-type TA-TFMB) was prepared from trimellitic anhydride chloride and 2,2′-bis(trifluoromethyl)benzidine (TFMB). A chemically imidized polyimide (PI) derived from TA-TFMB and TFMB was rather soluble in various solvents. Solution casting of this PI (TA-TFMB/TFMB) led to a flexible, non-turbid, and seemingly almost colorless PI film with a high T_g of 328 °C and a considerably low coefficient of thermal expansion (CTE) of 9.9 ppm K⁻¹ which results from significant in-plane chain orientation induced during solution casting. The self-orientation mechanism is discussed. The properties of TA-TFMB/TFMB were compared with those of some relevant systems. The results suggest that an electron-withdrawing effect of the 2,2′-CF₃ substituents of TA-TFMB and a twisted conformation of the central biphenyl moiety greatly contribute to the suppressed coloration of the TA-TFMB/TFMB film. The use of a TA-TFMB counterpart (ester-type TA-TFBP) was effective for further enhancing the transparency owing to reduced charge-transfer interaction. However, the thermal properties of TA-TFBP/TFMB were not always satisfactory. Copolymerization using 2,3,6,7-naphthalenetetracarboxylic dianhydride led to a PI film with an increased T_g of 277 °C and a very low CTE of 12.6 ppm K⁻¹ without significant decreases in the transparency and the solubility. Thus, this work proposes promising candidates as novel heat-resistant plastic substrate materials in display devices.     

Novel flexible chemical gas sensor based on poly(3,4-ethylenedioxythiophene) nanotube membrane

Poly(3,4-ethylenedioxythiophene) nanotubes (PEDOT NTs) flexible membrane was successfully fabricated by vapor deposition polymerization (VDP) mediated electrospinning for ammonia gas detection. PVA nanofibers (NFs) were electrospun as a core part and polyvinyl alcohol (PVA)/PEDOT coaxial nanocables (NCs) were prepared by VDP method via EDOT monomer adsorption onto the electrospun PVA NFs as templates. To obtain the PEDOT NTs membrane, the PVA NFs were removed from PVA/PEDOT coaxial NCs with distilled water. PVA/PEDOT coaxial NCs and PEDOT NTs had the conductivities of 71 and 61 S cm⁻¹ and were applied as a transducer for ammonia gas detection in the range of 1-100 parts per million (ppm) of NH₃ gas. They exhibited the minimum detectable level of ca. 5 parts per million (ppm) and fast response time (less than 1 s) towards ammonia gas. In a recovery time, the PEDOT NTs membrane sensor was ca. 30 s and shorter compared to that of the membrane sensor based on the PVA/PEDOT NCs (ca. 50 s). In addition, sensor performance of PEDOT NTs membrane was also undertaken as a function of membrane thickness. Thick membrane sensor (30 μm) had the enhanced sensitivity and the sensitivity on the membrane thickness was in the order of 30 μm > 20 μm > 10 μm at 60 ppm of NH₃ gas.     

Thermal stability of microencapsulated epoxy resins with poly(urea-formaldehyde)

A series of microcapsules filled with epoxy resins with poly(urea-formaldehyde) (PUF) shell were synthesized by in situ polymerization, and they were heat-treated for 2 h at 100 °C, 120 °C, 140 °C, 160 °C, 180 °C and 200 °C. The effects of surface morphology, wall shell thickness and diameter on the thermal stability of microcapsules were investigated. The chemical structure and surface morphology of microcapsules were investigated using Fourier-transform infrared spectroscope (FTIR) and scanning electron microscope (SEM), respectively. The thermal properties of microcapsules were investigated by thermogravimetric analysis (TGA and DTA) and by differential scanning calorimetry (DSC). The thermal damage mechanisms of microcapsules at lower temperature (<251 °C) are the diffusion of the core material out of the wall shell or the breakage of the wall shell owing to the mismatch of the thermal expansion of core and shell materials of microcapsules. The thermal damage mechanisms of microcapsules at higher temperature (>251 °C) are the decomposition of shell material and core materials. Increasing the wall shell thickness and surface compactness can enhance significantly the weight loss temperatures (T_d) of microcapsules. The microcapsules with mean wall shell thickness of 30 ± 5 μm and smoother surface exhibit higher thermal stability and can maintain quite intact up to approximately 180 °C.     

Thermal oxidation of polybutadiene. Part 1: Effect of temperature, oxygen pressure and sample thickness on the thermal oxidation of hydroxyl-terminated polybutadiene

An additive-free, uncrosslinked, hydroxyl-terminated polybutadiene of predominant trans 1-4 structure was thermally oxidized at temperatures ranging from 60 to 120 °C, under various oxygen pressures (between 0.01 and 3.1 MPa). Samples of thickness ranging from 5 to 1000 μm were studied by gravimetry (mass changes due to oxygen absorption) and infrared spectrophotometry (hydroxyl and carbonyl build-up, double bond consumption). The effects of film thickness, oxygen pressure and temperature on oxidation kinetics are discussed in terms of branched radical chain mechanisms.     

Electrohydrodynamic conduction pumps with cylindrical electrodes for pumping of dielectric liquid film in an open channel

In the present study, electrohydrodynamic conduction pumping of n-hexane and n-decane liquid films in an open channel has been investigated experimentally. These two dielectric liquids have nearly the same electrical properties but with their different viscosities. The effects of film thicknesses, the arrangement of electrodes and the gap between pumps on the flow rate of liquid films have been also studied. The pumps with cylindrical electrodes have been installed in the channel. The best performance of the conduction pumps, revealing with experimental results, has been achieved at 8 mm thickness of liquid film with the gap size of 55 mm for both dielectric liquids in the present layout of the pumps.     

Effects of chemical structure and precursor on optical properties,thermo-mechanical properties,and molecular orientation and order of thin films of stiff aromatic polyimides

Thin films of rigid poly(p-phenylene pyromellitimide) (PMDA-PDA) and semi-rigid poly(p-phenylene biphenyltetracarboximide) (BPDA-PDA), prepared by thermal imidization of the respective poly(amic acid) and poly(amic ethyl ester) precursors, were characterized with respect to their optical, thermomechanical and structural properties. Both polyimides exhibit an unusually large anisotropy between the in-plane and out-of-plane refractive indices, with n ranging from 0.198 to 0.216 for PMDA-PDA and from 0.230 to 0.242 for BPDA-PDA, nearly independent of the nature of the initial polyimide precursor, film thickness, and film preparation method. PMDA-PDA films exhibit low coefficients of thermal expansion (CTE's) of 6.5 and 8.2 ppm/C for the acid-derived and the ester-derived polyimides, respectively. In comparison, the BPDA-PDA films show CTE values of 4.3 and 18.0 for the acid-derived and ester-derived samples, respectively, despite the small differences in their optical anisotropies. Wide-angle x-ray diffraction patterns obtained in reflection and transmission for the various samples reveal a strong in-plane chain orientation for both PMDA-PDA and BPDA-PDA polyimides, with somewhat better intermolecular packing order for the ester-derived polyimide films. These effects of chemical structure and precursor on properties and structures of the polyimide films are discussed in light of recent theoretical considerations of semiflexible polymers.Dedicated to Prof E. W. Fischer on the occasion of his 65th birthday     

Effect of thickness on the thermal properties of hydrogen-bonded LbL assemblies

Layer-by-layer (LbL) assemblies have attracted much attention for their functional versatility and ease of fabrication. However, characterizing their thermal properties in relation to the film thickness has remained a challenging topic. We have investigated the role of film thickness on the glass transition temperature (T(g)) and coeffecient of thermal expansion for poly(ethylene oxide)/poly(acrylic acid) (PEO/PAA) and PEO/poly(methacrylic acid) (PEO/PMAA) hydrogen-bonded LbL assemblies in both bulk and ultrathin films using modulated differential scanning calorimetry (modulated DSC) and temperature-controlled ellipsometry. In PEO/PAA LbL films, a single, well-defined T(g) was observed regardless of film thickness. The T(g) increased by 9 °C relative to the bulk T(g) as film thickness decreased to 30 nm because of interactions between the film and its substrate. In contrast, PEO/PMAA LbL films show a single glass transition only after a thermal cross-linking step, which results in anhydride bonds between PMAA groups. The T(g), within error, was unaffected by film thickness, but PEO/PMAA LbL films of thicknesses below ~2.7 μm exhibited a small amount of PEO crystallization and phase separation for the thermally cross-linked films. The coefficients of thermal expansion of both types of film increased with decreasing film thickness.     

Activation energy for polypyrrole oxidation: film thickness influence

The oxidation rates of polypyrrole films at different temperatures fit Arrhenius plots, allowing the obtention of the activation energy for the reaction. The activation energy increases for rising thicknesses, up to 4 μm, of the polymer film and decreases for rising film thicknesses. Those values include the constant chemical activation energy and the energy required to relax the polymeric structure allowing the entrance of anions from the solution. The existence of a maximum on the polymeric relaxation energy points to a parallel change on the film molecular structure during the electropolymerization time. The variation of the diffusion coefficient per degree of temperature for the counterions, as a function of the film thickness, is similar to that obtained for the activation energy. Diffusion coefficients were obtained from the electrochemical stretched exponential describing a range of relaxation behaviors in disordered and non-equilibrium systems.